The use of digital processing circuitry, and apparatus including such circuitry, to perform a wide range of functions is pervasive in modern society. Repetitive functions carried out by such circuitry can be performed at rates much more quickly than the corresponding functions performed manually. Functions can be performed, for instance, to process large amounts of data at a rapid rate. Such processing of data sometimes includes reading data from, or writing data to, memory devices.
A digital computer system, for example, includes a computer main memory which provides storage locations from which data can be read or to which data can be written. A computer main memory is typically formed of a plurality of memory devices which together form the main memory. The computer main memory, for instance, is sometimes formed of a number of asynchronous DRAM (dynamic random access memory) integrated circuits. Some conventional computer memories includes faster, SRAM (static random access memory) integrated circuits. SRAM devices permit quicker access to the memory locations thereof by making a high speed, locally-accessed copy of the memory available to the CPU (central processing unit) of the digital computer system.
Some computer systems include a computer main memory formed of EDRAM (enhanced dynamic random access memory). An EDRAM forms a memory device in which an SRAM cache component and a DRAM component are integrated onto a single integrated circuit chip. The advantages of a the improved access speeds of an SRAM device is provided to permit the CPU of the computer system to access the memory locations thereof at high access rates.
Such aforementioned memory devices are formed of memory locations which form memory arrays. The memory locations of the memory arrays are identified by memory addresses. When a memory location of a memory array is to be accessed, the address of the memory location is provided to decoder circuitry which decodes the address signals applied thereto to permit the access to the appropriate memory locations. Conventionally, separate decoder circuitry is associated with each memory array of a memory device. When memory locations of a memory array are to be accessed, address signals applied to the decoder circuitry permit the appropriate memory locations of the memory array associated with the particular decoder circuitry to be accessed.
A significant design goal in the design and implementation of an integrated circuit is the minimization of the circuit area required to implement the circuit. Any manner by which to reduce the circuit area required to implement the circuit would facilitate the miniaturization of the circuit. The conventional use of separate decoder circuitry associated with each array of a multi-array memory device requires significant circuit area for its implementation.
A manner by which to address memory locations of any selected memory array of a multi-array memory device without requiring the memory device to include separate decoder circuitry associated with each memory array would advantageously permit the reduction in circuit area required to implement the memory device. While some existing techniques have been developed which permit sharing of decoder circuitry between more than one memory array, such existing techniques typically require extra decoder circuitry, as well as extra address or command lines, to effectuate the sharing of decoder circuitry.
It is in light of this background information related to memory devices that the significant improvements of the present invention have evolved.